GATHER (3)
A specified member of the group receives messages
from each member of the group and gathers these messages into
a single array.
SYNOPSIS
B
C int info = pvm_gather( void *result, void *data,
int count, int datatype, int msgtag,
char *group, int rootginst)
Fortran call pvmfgather(result, data, count, datatype,
msgtag, group, rootginst, info)
PARAMETERS
On the root this is a
pointer to the starting address of an array
datatype
of local values
which are to be accumulated from the members of the group.
If
n
if the number of members in the group, then this array
of
datatype
should be of length at least
n*count.
This argument is meaningful only on the root.
For each group member this is a pointer to the starting
address of an array of length
count
of
datatype
which will be sent to the specified root member of the group.
Integer specifying the number of elements of
datatype
to be sent by each member of the group to the root.
Integer specifying the type of the entries in the result and data arrays.
(See below for defined types.)
Integer message tag supplied by the user.
msgtag should be >= 0. It allows the user's program to
distinguish between different kinds of messages.
Character string group name of an existing group.
Integer instance number of group member who performs the
gather of the messages from the members of the group.
Integer status code returned by the routine.
Values less than zero indicate an error.
DESCRIPTION
C datatypes FORTRAN datatypes
-----------------------------------
PVM_BYTE BYTE1
PVM_SHORT INTEGER2
PVM_INT INTEGER4
PVM_FLOAT REAL4
PVM_CPLX COMPLEX8
PVM_DOUBLE REAL8
PVM_DCPLX COMPLEX16
PVM_LONG
In using the scatter and gather routines, keep in mind that
C stores multidimensional arrays in row order,
typically starting with an initial index of 0; whereas,
Fortran stores arrays in column order,
typically starting with an offset of 1.
Note: pvm_gather() does not block. If a task calls pvm_gather and then
leaves the group before the root has called pvm_gather an error may occur.
The current algorithm is very simple and robust. A future implementation
may make more efficient use of the architecture to allow greater
parallelism.
EXAMPLES
C:
info = pvm_gather(&getmatrix, &myrow, 10, PVM_INT,
msgtag, "workers", rootginst);
Fortran:
CALL PVMFGATHER(GETMATRIX, MYCOLUMN, COUNT, INTEGER4,
& MTAG, 'workers', ROOT, INFO)
ERRORS
These error conditions can be returned by
pvm_gather
Calling task is not in the group
The datatype specified is not appropriate
SEE ALSO
pvm_bcast(3PVM) pvm_barrier(3PVM) pvm_psend(3PVM)
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